Start with the performance target
A double-glazed unit has two glass panes; a triple-glazed unit has three. Coatings, cavity construction, spacers and the frame all contribute to the final assembly’s performance.
For a useful comparison, ask for the whole-window U-factor using the same units and rating method. A lower U-factor indicates lower heat transfer. A centre-of-glass value describes the glass area and should not be treated as the complete window rating.
Compare the complete package
| Consideration | Ask your supplier |
|---|---|
| Thermal performance | What is the whole-window U-factor for the proposed assembly? |
| Solar gain | How does the SHGC suit the orientation and shading? |
| Daylight & appearance | How will the proposed glass affect visible light, colour and reflection? |
| Glass weight | Is the build-up compatible with the panel size, hardware and handling plan? |
| Safety & sound | Which glass construction addresses the project’s specific requirements? |
Solar gain is a separate decision
Solar Heat Gain Coefficient, or SHGC, describes the fraction of solar heat admitted through the product. Review it with the project’s orientation, shading and heating and cooling strategy. More panes do not automatically mean the right solar control for every elevation.
Consider the room as well as the glass
A bedroom, a large west-facing living space and a sheltered stairwell may have different priorities. Tell us about privacy, daylight, views and any acoustic goals before choosing the build-up.
Discuss condensation with the complete indoor environment in mind. Indoor humidity, airflow and surface temperature can all influence whether condensation forms; changing pane count is not a guarantee that it will disappear.
Make the choice with your drawings
Send the elevation, glass dimensions and performance targets. We can compare a suitable double- or triple-glazed specification for the selected system and explain how the options affect the package.
Continue reading: our performance glossary and glazing selection notes.